This invention is in the field of devices for retrieving loose articles from wells.
In drilling wells such as deep oil wells or the like, tools or other loose articles sometimes fall to the bottom of the well and drilling cannot continue while those articles remain therein. Occasionally a toothed cone of a rotary drill bit will become detached or broken and impede further drilling, making it necessary to remove the loose piece. Many devices have been proposed for retrieving tools or other loose articles from the bottom of such wells. See, for example, the U.S. Pat. Nos. to Lang 2,709,617, Sutliff 2,505,073, Fitzpatrick 1,775,340, and Steele 3,152,829. The Lang patent provides a tubular body having a piston slidable therein and spring fingers projecting downwardly from the piston along the inner periphery of the tubular body. Camming means at the bottom periphery of the tubular body cause the spring fingers to flex inwardly as the piston is forced down and, hopefully, grip and retain a loose article in the bottom of the well. A loose ball can be dropped through the drill string to close an opening in the piston and serve as a valve to trap drilling mud above the piston to effect downward movement. The spring fingers of this device, however, are flexed a great amount and breakage is likely to occur. Furthermore, as the piston moves downwardly the spring fingers scrape along the bottom of the well and could become engaged with the rock formation, preventing satisfactory operation. The Sutliff and Fitzpatrick devices propose pivoted fingers and a relatively complex mechanism for swinging them inwardly to grasp a loose article in the well but in these devices also the fingers can scrape along the bottom of the well and thus are subject to malfunction. The Steele patent is designed for a special purpose, that is, the removal of a tool having a particular upper formation and relies on the resiliency of spring fingers to close them on the tool.
The devices referred to above are not completely satisfactory when a loose article is to be removed from a well.